Monopole and dipole antennas are well-known in the prior art. For such antennas, it is often desirable to improve upon the portability aspect of such antennas (i.e., make the antenna smaller) without significantly degrading antenna performance. In the case of dipole antennas, it may be desirable to design the antenna so that it has a feed structure that is identical to the feed structure of a monopole antenna. This can allow for a simpler means of balancing the feed.
A candidate antenna element that could satisfy these requirements while allowing for a reduction in antenna height could be a resonant-cavity leaky-wave antenna. An advantage of a resonant-cavity leaky-wave monopole (or dipole) antenna can be that the input impedance of the antenna can be highly dependent on the input impedance of the cavity. In the case that the cavity is a terminated waveguide, this impedance is largely a function of the characteristic impedance of the waveguide. The design challenge can then be to efficiently couple energy from the feed structure into the cavity and then to leak that energy out of the cavity through the aperture(s). Additionally, the aperture could be designed such that the induced leakage current radiates energy as would a standard monopole (or dipole). The proposed design methodology can allow an antenna designer to ensure both these requirements are satisfied.
In view of the above, it is an object of the present invention to provide a leaky-wave antenna that is significantly smaller than its prior art counterpart, but without sacrificing the bandwidth, gain, and radiation patterns of the antenna. Another object of the present invention is to provide a leaky-wave antenna that can allow the same feed structure for both monopole and dipole antenna. Yet another object of the present invention is to provide a leaky-wave antenna that is electrically short relative to its prior art counterparts. Still another object of the present invention is to provide a leaky-wave antenna with a design methodology that can be frequency scalable, which can allow for easy design modifications if the desired operating parameters of the antenna are changed. Yet another object of the present invention is to provide a leaky-wave antenna that is easy to manufacture in a cost-effective manner.